ELOG - Coil driver noise re-measurement

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Mon Mar 19 23:44:00 2018, gautam, Update, IOO, IMC loop checkup

Tue Mar 20 16:53:03 2018, gautam, Update, IOO, IMC loop checkup

Tue Mar 20 21:08:03 2018, gautam, Update, IOO, IMC loop checkup

Tue Mar 20 22:44:45 2018, gautam, Update, IOO, IMC loop checkup

Wed Mar 21 15:52:45 2018, gautam, Update, IOO, MC error point calibration

Wed Mar 21 17:31:21 2018, gautam, Update, IOO, MC error point calibration

Wed Mar 21 21:13:44 2018, gautam, Update, IOO, IMC noise budget

Tue Mar 27 01:39:44 2018, gautam, Update, IOO, PSL noise eater was off

Tue Mar 27 19:32:03 2018, arijit, Update, IOO, PSL noise eater was off

Tue Mar 27 23:37:35 2018, gautam, Update, IOO, MC REFL PD removed

Wed Mar 28 21:31:39 2018, gautam, Update, IOO, MC REFL PD removed

Wed Mar 28 21:47:37 2018, arijit, Update, IOO, MCREFL_PD Optical response measurement

Thu Mar 29 17:57:36 2018, arijit, Update, IOO, MCREFL_PD Optical response measurement

Fri Mar 30 06:14:31 2018, rana, Update, IOO, MCREFL_PD Optical response measurement

Fri Mar 30 22:37:36 2018, Kevin, Update, IOO, MCREFL_PD Optical response measurement

Thu Apr 5 04:36:56 2018, Kevin, Update, IOO, Coil driver noise

Thu Apr 5 12:13:18 2018, Koji, Update, IOO, Coil driver noise

Fri Apr 6 21:39:09 2018, gautam, Update, IOO, MC2 suspension health checkup

Mon Apr 9 18:46:03 2018, gautam, Update, IOO, Further debugging

Tue Apr 10 14:28:44 2018, gautam, Update, IOO, Further debugging

Wed Apr 11 01:34:31 2018, gautam, Update, IOO, Activities today

Thu Apr 12 18:12:49 2018, gautam, Update, ALS, NPRO channels hijacked

Fri Apr 13 11:02:41 2018, gautam, Update, ALS, EX fiber polarization drift

Fri Apr 13 17:56:26 2018, gautam, Update, ALS, Fibers switched out

Sat Apr 14 14:42:09 2018, gautam, Update, ALS, Fibers switched out

Tue Apr 17 14:08:29 2018, gautam, Update, ALS, Fibers switched out

Fri Apr 20 00:26:34 2018, gautam, Update, ALS, Fibers switched out

Sat Apr 21 20:25:12 2018, gautam, Update, ALS, PSL fiber pickoff status

Thu Apr 19 00:03:51 2018, gautam, Update, IOO, More IMC NBing

Thu Apr 19 17:15:35 2018, gautam, Update, IOO, More IMC NBing

Sun May 20 23:43:50 2018, gautam, Update, IOO, Coil driver noise re-measurement

Tue May 22 17:26:25 2018, gautam, Update, IOO, MC1 Coil Driver pulled out

Tue May 22 23:28:01 2018, gautam, Update, IOO, MC1 Coil Driver pulled out

Wed May 23 17:58:48 2018, gautam, Update, IOO, MC1 Coil Driver pulled out

Wed May 30 10:17:46 2018, gautam, Update, IOO, MC1 Coil Driver pulled out

Fri Apr 6 22:23:53 2018, Kevin, Update, IOO, Coil driver noise

Message ID: 13870 Entry time: Sun May 20 23:43:50 2018 In reply to: 13770 Reply to this: 13878

Author:	gautam
Type:	Update
Category:	IOO
Subject:	Coil driver noise re-measurement

Summary:

In the IMC actuation chain, it looks like the MC1/MC3 de-whitening boards, and also all three MC optics' coil driver boards, are showing higher noise than expected from LISO modeling. One possible candidate is thick film resistors on the coil driver boards. The plan is to debug these further by pulling the board out of the Eurocrate and investigating on the electronics bench.

Why bother? Mainly because I want to see how good the IR ALS noise is, and currently, the PSL frequency noise is causing the measurement to be worse than references taken from previous known good times.

Details:

Sometime ago, rana suggested to me that I should do this measurement more systematically.

Attachments #1, #2 and #3 show noise measurements in various conditions for MC1, MC2 and MC3 respectively.
In the above three attachments, I stitched together multiple spans from the SR785, and so the bin-width is different. The data is downloaded from the analyzer normalized by the bin-width (PSD units).
The roll-off at ~800Hz in the orange trace for MC1 and MC3 is consistent with an 800 Hz LPF that was used for anti-image filtering from the old 2 kHz era.
While it may look like the analog de-whitening isn't being switched on in some of these plots, I confirmed by transfer function measurement that it is indeed switching.
Data used to make these plots are in Attachment #4. Unfortunately, the code requires some of my personal plotting libraries and so I'm not uploading it.
Sketch of measurement setup is shown in Attachment #5. It is not indicated in the schematic, but the SR560 was operated in battery mode for this measurement.
For MC1, I did the additional measurement of terminating the LEMO input to the coil driver and measuring (what should have been) just the coil driver electronics noise. But this measurement doesn't look very clean, and hence, the decision to pull the board out to continue debugging.
While at 1X6, Rana tightened the LEMO connectors going to MC1. We should opportunistically do MC2 and MC3 as well.
Some changes to be made:
- Thick film ---> thin film.
- Reroute HPF-ed back-plane Vmon output to the front panel LEMO.